高压物理学报

Shock Temperature Measurement for Metals (Ⅳ)－'Three Layer Model' and Its Application

TAN Hua, DAI Cheng-Da

2000, 14(2): 81-91 . doi: 10.11858/gywlxb.2000.02.001

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Abstract:
Effects on shock temperature measurements of the gap between the bulk metal sample and the transparent window are specially discussed in detail. A three-layer model corresponding to the bulk metal sample/gap/transparent window target-sample assembly is proposed. A universal analytical solution of the heat conduction equation of this three-layer model is obtained. The model is applied successfully to studies in radiometry shock-temperature measurements, to the analyses of the thermal resistance model and of the heat conductivity measurement of the window materials at very high pressures. Special efforts are focused on the principle and the possibility of utilizing a bulk sample rather than a film in the radiometry shock temperature measurements for metals. Based on the three-layer model, the sharp peak appearing at the beginning of the sample/window interface temperature profile will drop down at first rapidly in a few tens of nanoseconds. Then it will approach slowly to a level close to the equilibrium temperature predicted by the ideal interface model, if the width of the gap is less than 1 micron (0.5 micron less will be the better). It is therefore possible to use a lumpy sample (rather than) a film to conduct shock temperature measurement. We presented here some preliminary experimental records for the shock temperature measurement obtained by using the lumpy ironmeteorite samples, which demonstrated the feasibility of the technique. Also discussed here are the basic problems existing in the so-called thermal resistance model. Applying the analytical solution of the three-layer model according to the conditions specified by the thermal resistance model, we obtained a result contradictory both to experimental observations and to the expectation of the thermal resistance model. An insight into the thermal resistance model reveals the paradox in the basic assumptions of the model itself.

High-Pressure Raman Study of Non-Linear Optical Crystals

Shen Ze-Xiang

2000, 14(2): 92-98 . doi: 10.11858/gywlxb.2000.02.002

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Abstract:
In this presentation, we report on the high-pressure Raman spectroscopic studies of some non-linear optical crystals, e. g. KNbO3 (KN), KIO3 (KI) and KTiOAsO4 (KTA), which are important for both their practical applications and theoretical values. The effect of pressure on KN is extremely large and there exist a rich variety of pressure-induced changes. Mode softening is found for some of the characteristic Raman bands. Intensity transfer and frequency repelling have been observed in the 200 cm-1 region as a result of strong coupling between two B1 (TO) modes, whose frequencies have been brought closer under pressure. There are three new crystalline and an amorphous phases, and two of the phase transitions are of displace type. Three first-order pressure-induced phase transitions are inferred for KTA. The first takes place at 3.2 GPa, indicated by drastic spectral changes related to TiO6 octahedral. The second occurs at 7.5 GPa involving both TiO6 and AsO4 groups. Several modes belonging to TiO6 also soften between 0～7.5 GPa. The third phase transition occurs near 10 GPa and the high-pressure phase should be of higher symmetry. Drastic spectral changes and phase transitions are observed for KI up to 32 GPa. The first transition occurs at 5.0 GPa characterized by major spectral changes of the 1, 2, and 4 modes. The other transitions are found at 8.7, 15 and 22 GPa. The phase that is stable between 15～22 GPa has a higher symmetry than the phases in the lower pressures. The IO3 pyramidal ions may have lost their identity and changed to IO6 octahedral above 22 GPa.

An Experimental Study of the Effects of DDT Tube Materials on the Deflagration to Detonation Transition in Granular RDX Bed

ZHAO Tong-Hu, ZHANG Shou-Qi, ZHANG Xin-Yan, ZHAO Feng, HE Zhi

2000, 14(2): 99-104 . doi: 10.11858/gywlxb.2000.02.003

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Abstract:
The effects of DDT tube materials on deflagration to detonation transition in granular RDX bed ignited by an igniter and an ignition charge have been experimentally studied with self-short (capped) and coaxial ionization pins.

The Synthesis of La1-xNaxTiO3 under High-Pressure and High-Temperature and Its Spectra Study

MIAO Ji-Peng, LI Li-Ping, Lü Zhe, CHE Yu-Lu, SONG Yan-Bin, LU Da-Yong, XU Da-Peng, LIU Hong-Jian, SU Wen-Hui, ZHENG Ying-Guang

2000, 14(2): 105-110 . doi: 10.11858/gywlxb.2000.02.004

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Abstract:
Perovskite oxides of La1-xNaxTiO3 with mixed valence were synthesized under high-pressure and high-temperature. XRD measurement shows that the samples belong to distorted cubic perovskite structure. Volumes of samples decrease as x increases. XPS and EPR measurements indicate that Ti ions are mixed valence of +3 and +4 and vacancy of A-site ions exists. The valence state of Ti ions can be altered by high-pressure and high-temperature. IR measurement indicates that the frequency for vibration of Ti－O bond increases as x increase.

The Synthesis of High-Pressure Phase of BN: E-BN, w-BN, c-BN by Physical Vapor Deposition Method

ZHU Pin-Wen, ZHAO Yong-Nian, ZOU Guang-Tian, HE Zhi

2000, 14(2): 111-114 . doi: 10.11858/gywlxb.2000.02.005

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Abstract:
In this paper we report that we have obtained the E-BN film that was named after the method by which it was obtained (E=Explosion). During the BN films deposition, we suggest a model of phase transition from E-BN to c-BN. We can explain the c-BN nucleation during the deposition by this model. The film we obtained has very good adhesion due to the phase transition.

Opacities in Au Plasmas

YANG Xiang-Dong, CHENG Xin-Lu, MENG Chuan-Min, YANG Li, WANG Fan-Hou

2000, 14(2): 115-118 . doi: 10.11858/gywlxb.2000.02.006

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Abstract:
Under local thermodynamic equilibrium conditions (LTE), the STA (super transition array) model was used to calculate the parameters of the transition arrays of Au plasmas under certain temperature and density, and also radiative opacity of plasmas under shock loading.

Study on the Property of Nanometric Diamond Particles under High Temperature and High Pressure

WEN Chao, ZHOU Gang, HAO Zhao-Yin, SUN De-Yu, LI Xun, LIU Xiao-Xin, SHI Xiao-Feng, HUO Hong-Fa

2000, 14(2): 119-124 . doi: 10.11858/gywlxb.2000.02.007

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Abstract:
Under high temperature (1 000～1 600 K) and high pressure (5.2 GPa) with Ni70Mn25Co5 (100#) being the catalyst, the growing behavior of nanometric diamond particles (2～10 nm) synthesized by the detonation of the explosives has been investigated. The effects of growing conditions on the microstructure and property of sintered nanometric diamond were studied. The samples compressed with nanometric diamond powder and Ni70Mn25Co5 (100#) alloy powder and the disks of Ni70Mn25Co5 (100#) alloy were put in the synthesis reaction cell on alternate. The results indicate that the nanometric diamond powder did not grow, but convert to graphite under high temperature and high pressure. Under the same high pressure and holding time, the degree of graphitization of nanometric diamond powders begin to decrease with the temperature decreasing, and nanometric diamond powders begin to grow. Diamond particles with the diameter of 0.1 mm can be acquired under high temperature (1 070 K) that the ordinary graphite doesn't convert to diamond and the ordinary diamond crystal will convert to graphite. This phenomenon shows that the nanometric diamond particles can grow into larger diamond particles under lower temperature because of the surface activity of nanometric particles.

Studied on the IR Spectra of Floating Shocked and Polarized Adsorbed Minerals

DONG Fa-Qin, SONG Gong-Bao, WAN Pu, PENG Tong-Jiang, LI Ping, LI Guo-Wu, FENG Qi-Ming

2000, 14(2): 125-132 . doi: 10.11858/gywlxb.2000.02.008

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Abstract:
In this paper the authors compare the IR spectra feature and their change of seven main mineral micro-particles, and analyze their mechanical-structure effect and the surface group transform process after their surfaces being shocked with M3.0 or adsorbed substance with moment of dipole 2.0.

The Effect of Initial Density on Radiation Characteristics of the Wave Front

HONG Yan-Ji, TAN Hua, JIN Xing

2000, 14(2): 133-138 . doi: 10.11858/gywlxb.2000.02.009

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Abstract:
A set of numerical radiation hydrodynamics computation of the structure of strong waves in neon is described. The effect of initial density on spectral and special dependence on the radiation characteristics and the luminosity temperature of the wave front have been taken into account in detail.

Numerical Simulations of Hypervelocity Launchers

LIN Shao-Ming, XU Nan-Xian, CHEN Dong-Quan

2000, 14(2): 139-145 . doi: 10.11858/gywlxb.2000.02.010

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Abstract:
Hypervelocity launchers (HVL) were simulated using a two-dimensional Lagrangian finite element code EPFT101. In the simulation model, a graded-density assembly is used to prevent the melting and fracturing of flier plates. Barrel extension method is adopted to increase launch velocity. The parameters of HVL were also optimized. As an example, the final velocity of a 1.063 gram titanium alloy flier plate impacted by a graded-density assembly at 5.8 km/s was predicted to be about 10 km/s.

Experimental Observation of Shock Waves Driven with 0.35 m Laser

JIANG Shao-En, LI Wen-Hong, DING Yong-Kun, LIU Yong-Gang

2000, 14(2): 146-150 . doi: 10.11858/gywlxb.2000.02.011

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Abstract:
Experimental records of the light emitting from heating luminescence at the rear surface of wedge-shaped aluminum target were obtained by an optical streak camera. The target was irradiated by a focused high power laser beam with 0.35 m wavelength. The scaling relation between shock wave pressure and velocity was determined using wedge-shaped samples. The experimental results showed that shock wave pressure was close to the pressure estimated from the scaling relation.

Deformation and Breakup of Droplets behind Shock Wave

LU Shou-Xiang, QIN You-Hua

2000, 14(2): 151-154 . doi: 10.11858/gywlxb.2000.02.012

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Abstract:
A comprehensive model of deformation and breakup of droplets behind a shock is developed according to the dynamics of single particle in the paper. The concept of time for drop firstly misting is applied to analyze the characteristics of the processes of droplet deformation and breakup induced by a shock wave. It is shown that the droplet deformation accelerates after a shock has passed and then mists on the surface of the deformed droplet and breaks up completely. The results of the rate of the droplet deformation and the time for droplet breakup analyzed by the present model are in accord to the reported experimental results.

Shock Temperature Measurement of Transparent Materials

HU Jin-Biao, TANG Zhi-Ping, TAN Hua

2000, 14(2): 155-160 . doi: 10.11858/gywlxb.2000.02.013

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Abstract:
Under shock compressions, a few special crystal materials have very small absorptance. This means that although they stand in high temperature states on, temperatures can not be detected by using optical radiation techniques because of the low emissivity. In this paper, an optical radiation technique for measuring temperature of very low emissive material under shock compression is proposed based on the analysis of the thermal diffusion at the interface of sample and thin film. To test this technique, temperature of crystal NaCl at shock pressure 41 GPa was measured. The result agrees with the results of Kormer, et al. This shows that this technique is feasible and can be used to measure shock temperatures of low emissive materials.

2000 Vol. 14, No. 2

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